TN 

948 

R3L6 


Idnd 

Tha  Radium-Uranium  Ratio 
in  Carnotites 


THE  LIBRARY 
OF 

THE  UNIVERSITY 

OF  CALIFORNIA 

LOS  ANGELES 


The  RALPH  D.  REED  LIBRARY 

DEPARTMENT  OP  fiCTtLOGY 

UNIVERSITY  of  CALIFORNIA 

LOS  AN<;"5l.r^.  '  ALIP. 


TN 

I  3 


inical  Paper  88  Mineral  Technology  6 

DEPARTMENT  OF   THE    INTERIOR 
BUREAU    OF    MINES 

JOSEPH  A,  HOLMES,  DIRECTOR 


THE  RADIUM-URANIUM  RATIO 
IN  CARNOTITES 


S.  C.  LIND  AND  C.  F.  WHITTEMORE 


of 


.     /      - 


SRSITY  of  C 
LOS  ANGELES,  CA 


__ _  . 


PROPERTY  OF 
OGY  DEPART* 

LOS  ANGELES 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 
1915 


The  Bureau  of  Mines,  in  carrying  out  one  of  the  provisions  of  its  organic  act — to 
disseminate  information  concerning  investigations  made— prints  a  limited  free  edition 
of  each  of  its  publications. 

When  this  edition  is  exhausted  copies  may  be  obtained  at  cost  price  only  through 

the  Superintendent  of  Documents,  Government  Printing  Office,  Washington,  D.  C., 

who  is  the  authorized  agent  of  the  Federal  Government  for  the  sale  of  all  publications. 

The  Superintendent  of  Documents  is  not  an  official  of  the  Bureau  of  Mines.    His  is 

an  entirely  separate  office  and  he  should  be  addressed: 

SUPERINTENDENT    OF    DOCUMENTS, 
Government  Printing  Office, 

Washington,  D.  C. 

The  general  law  under  which  publications  are  distributed  prohibits  the  giving  of 
more  than  one  copy  of  a  publication  to  one  person.  Additional  copies  must  be  pur- 
chased from  the  Superintendent  of  Documents.  The  price  of  this  technical  paper  is 
5  cents. 

First  edition.     March,  1915. 


Geology 
Library 

TN 


CONTENTS. 

Introduction i 

Work  of  other  investigators 

Variations  of  ratio  in  minerals  other  than  pitchblende 

Constancy  of  the  ratio  in  pitchblendes 

The  ratio  in  carnotites g 

Description  of  samples g 

Discussion  of  methods  used 9 

The  emanating  power  of  carnotite 10 

Impracticability  of  solid-ore  radiation  method  for  carnotite 12 

Emanation -method  for  the  determination  of  radium 12 

Solution  method 12 

Solution  emanation  method  in  a  single  operation ' 12 

Solution  and  boiling  off  emanation 14 

Fusion  method 14 

Fusion-and-solution  method 15 

Ignition  method -. 16 

Electroscopic  determination  of  radium. W 

Electroscope  with  detachable  ionization  chamber 17 

Standardization  of  electroscopes 19 

Data  for  standard  pitchblende 20 

Control  of  standardization 20 

Procedure  in  using  the  electroscope 20 

The  determination  of  uranium 21 

Gravimetric  method  for  vanadium  and  uranium  in  carnotite 21 

Separation  of  alumina 22 

Results  of  experiments 23 

Discussion  of  results 26 

Summary 28 

Acknowledgment 28 

Publications  on  mineral  technology 29 


ILLUSTRATIONS. 


PLATE  I.  A,  View  of  electroscope  with  interchangeable  ionization  chambers; 
B,  Ionization  chamber  detached  from  instrument  and  cap  in 
place 

FIGURE  1.  Apparatus  for  determining  emanation  by  sealed-tube  method 

2.  Apparatus  for  dissolving  carnotite  and  collecting  the  emanation — 

3.  Sulphuric-acid  microdrying  bulb 

4.  Cross  section  of  electroscope  with  detachable  ionization  chamber. ..        18 


Geology 
Library 


THE  RADIUM-URANIUM  RATIO  IN  CARNOTITES. 


By  S.  C.  LIND  and  C.  F.  WHITTEMORE. 


INTRODUCTION . 

One  of  the  recent  investigations  undertaken  by  the  Bureau  of 
Mines,  in  pursuance  of  its  endeavors  to  increase  efficiency  in  the 
mining  and  treatment  of  the  mineral  resources  in  the  United  States, 
deals  with  methods  of  lessening  waste  in  the  extraction  of  radium 
from  the  carnotite  and  other  uranium-bearing  minerals  of  Colorado 
and  Utah.  In  the  course  of  this  investigation  it  has  been  necessary 
to  study  the  physical  and  chemical  properties  of  these  ores  and  to 
determine  the  radium  and  uranium  content  of  many  samples. 

The  radium-uranium  ratio  in  different  uranium  minerals  has  been 
determined  by  various  investigators,  and  among  such  minerals  carno- 
tite has  naturally  been  included,  though  hi  rather  surprisingly  few 
instances.  The  general  constancy  of  the  ratios  between  the  quantity 
of  radium  and  that  of  uranium  hi  most  uranium  minerals  may  be 
regarded  as  definitely  established.  The  bearing  of  this  experiment- 
ally demonstrated  fact  on  the  theory  of  the  source  of  radium  in  a 
series  of  atomic  disintegrations  from  the  parent  element  uranium 
needs  no  comment. 

Although  the  ratios  so  determined  have  been  in  the  main  constant 
and  agree  well  in  absolute  value  with  what  is  to  be  expected  theo- 
retically from  other  radioactive  measurements,  still  in  some  instances 
there  have  been  rather  large  deviations  and  the  explanations  offered 
for  these  must  be  regarded  as  only  partly  satisfactory.  The  devia- 
tions have  usually  been  in  the  direction  of  low  ratios  of  radium  to 
uranium,  though  deviations  in  the  opposite  direction  have  also  been 
reported.  •  ; 

In  so  far  as  deviations  from  the  normal  radium-uranium  ratio  have 
been  found  for  carnotite,  these  hitherto  have  been  invariably  low  and 
the  impression  seems  to  have  become  rather  general,  particularly 
abroad,  that  carnotite,  as  a  rule,  contains  anywhere  from  a  few  per 
cent  to  30  per  cent  less  radium  than  would  correspond  to  its  uranium 
content.  It  therefore  became  a  matter  of  some  theoretical  interest 
to  determine  the  ratio  for  a  larger  number  of  samples  of  carnotite 
than  had  been  investigated. 


1019021 


6  THE   RADIUM-URANIUM    RATIO   IN   CARNOTITES. 

The  determination  of  the  ratio  in  carnotites  has  also  practical 
value  because  of  the  increasing  importance  of  carnotite  as  the  largest 
known  source  of  radium.  The  practice  has  been  and  is  to  buy  and 
sell  these  ores  on  the  basis  of  their  percentage  of  uranium  oxide 
(U3O8),  although  European  buyers  have  sometimes  insisted  on  mak- 
ing allowance  for  a  supposed  deficiency  in  radium.  It  is  evidently  of 
the  greatest  importance  in  determining  what  is  the  justification  for 
such  practice  to  know  within  what  limits  the  radium  content  is  fixed 
by  the  uranium  content.  With  a  view  to  determining  these  limits 
the  investigation  reported  in  this  paper  was  undertaken. 

WORK  OF  OTHER  INVESTIGATORS. 

For  the  first  experimental  demonstrations  of  the  constancy  of  the 
radium-uranium  ratio  we  are  indebted  to  the  work  of  Boltwood/1 
Rutherford,6  Strutt,c  McCoy/  and  Eve.« 

VARIATIONS  OF  RATIO  IN  MINERALS  OTHER  THAN  PITCHBLENDE. 

Later  it  began  to  be  recognized  that  certain  uranium  minerals  of 
secondary  origin,  of  which  autunite  [Ca(UO2)2(PO4)2.8H2O]  is  one 
of  the  chief  representatives,  show  a  radium-uranium  ratio  below 
that  of  pitchblende.  In  1909  Mile.  Gleditsch-''  announced  that  she 
had  found  a  sample  of  French  autunite  showing  only  about  80  per 
cent  of  the  normal  (pitchblende)  ratio.  A  low  ratio  for  autunite  was 
confirmed  in  1910  by  Russell/  who  found,  also  in  a  sample  of  French 
autunite,  a  ratio  only  27  per  cent  of  the  normal;  while  Soddy  and 
PirretA  about  the  same  time  found  that  the  ratio  for  a  sample  of 
Spanish  autunite  was  44.5  per  cent  of  the  pitchblende  ratio. 

To  account  for  these  low  ratios  in  a  sense  consistent  with  the 
Rutherford  and  Soddy  theory  of  radioactivity,  two  different  explana- 
tions have  been  proposed.  One  assumes  that  the  secondary  minerals 
are  too  young  for  the  quantity  of  radium  to  have  accumulated  to  the 
maximum  equilibrium  value  shown  hi  older  minerals  such  as  pitch- 
blende. The  other  explanation  assumes  that  the  secondary  minerals, 

a  Boltwood,  B.  B.,  The  origin  of  radium:  Philos.  Mag.,  vol.  9, 1905,  pp.  599-613;  On  the  ratio  of  radium 
to  uranium  in  some  minerals:  Am.  Jour.  Sci.,  ser.  4,  vol.  18, 1904,  pp.  97-103;  On  the  radioactivity  of  ura- 
nium minerals:  Am.  Jour.  Sci.,  ser.  4,  vol.  25, 1908,  pp.  269-298. 

6  Rutherford,  E.  E.,  and  Boltwood,  B.  B.,  The  relative  proportion  of  radium  and  uranium  in  radioactive 
minerals:  Am.  Jour.  Sci.,  ser.  4,  vol.  20, 1905,  pp.  55-56;  vol.  22, 1906,  pp.  1-30. 

cStrutt,  R.  J.,  On  the  radioactive  minerals:  Proc.  Roy.  Soc.  London,  ser.  A,  vol.  76, 1905,  pp.  88-101; 
Note  supplementary  to  paper,  vol.  76,  p.  312. 

d  McCoy,  H.  N.,  Ueber  das  Entstehen  des  Radiums:  Ber.  Deutsch.  chem.  Gesell.,  Jahrg.  37,  Bd.  4, 
1904,  pp.  2641-2656;  Radioactivity  as  an  atomic  property:  Jour.  Am.  Chem.  Soc.,  vol.  27,  pt.  1, 1905,  p.  391. 

e  Eve,  A.  8.,  The  measurement  of  radium  in  minerals  by  the  r-radiation:  Am.  Jour.  Sci.,  ser.  4,  vol.  22, 
1906,  pp.  4-7. 

/  Gleditsch,  Ellen,  Sur  le  radium  et  1'uranium  contenus  dans  les  mine'raux  radioactifs:  Compt.  rend., 
1. 148, 1909,  p.  1451;  Sur  le  rapport  entre  1'uranium  et  le  radium  dans  les  mhuJraux  radioactifs:  1. 149, 
1909,  p.  267. 

e  Russell,  A.  S.,  The  ratio  between  radium  and  uranium  in  minerals:  Nature,  vol.  84, 1910,  pp.  238-239. 

»  Soddy,  Frederick,  and  Pirret,  Ruth,  The  ratio  between  radium  and  uranium  in  minerals:  Philos.  Mag., 
voL  20, 1910,  pp.  345-349;  vol.  21, 1911,  pp.  652-658. 


WORK   OF   OTHER  INVESTIGATORS.  7 

because  of  a  looser  mechanical  structure,  are  more  easily  leached  by 
water  and  that  radium  is  more  readily  removed  than  uranium,  so  that 
the  ratio  of  radium  to  uranium  is  diminished  by  this  process. 

Additional  evidence  adduced  principally  by  Marckwald  and  Rus- 
sell a  appears  to  support  the  leaching  theory,  for  in  autunite  the 
ionium-uranium  ratio  was  found  to  approach  the  theoretical  value 
much  more  nearly  than  does  the  radium-uranium  ratio,  thus  indicat- 
ing a  removal  of  radium,  whereas  lead,  one  of  the  end  products  of 
the  uranium  family,  was  found  to  be  almost  entirely  lacking. 

At  the  same  time  that  Mile.  Gleditsch b  announced  the  existence 
of  a  low  radium-uranium  ratio  in  autunite  she  reported  a  high  ratio 
(about  16  per  cent  high)  in  thorianite  from  Ceylon.  Explaining  a 
high  ratio  appeared  to  present  much  more  formidable  difficulties  than 
explaining  low  ones.  Mile.  Gleditsch  favored  the  view  that  either 
ionium  or  some  unknown  member  between  uranium  and  radium  had 
a  much  longer  period  than  was  previously  supposed,  necessitating 
a  greater  lapse  of  time  for  the  attainment  of  equilibrium.  Conse- 
quently, according  to  this  view,  all  the  uranium  minerals  would  be 
slowly  advancing  to  an  equilibrium  content  of  radium  higher  than 
that  in  most  pitchblendes. 

The  view  held  by  Mile.  Gleditsch  did  not  find  general  acceptance. 
Soddy  and  Pirretc  had  also  examined  autunite,  pitchblende,  and 
thorianite,  and,  although  confirming  a  low  ratio  for  autunite,  as 
already  stated,  they  failed  to  find  a  difference  between  the  latter 
two  exceeding  3  per  cent,  which  they  regarded  as  within  their  limits 
of  experimental  error. 

In  a  later  investigation  extended  to  a  much  larger  number  of 
uranium  minerals  Mile.  Gleditsch  d  confirmed  her  earlier  results,  find- 
ing ratios  of  radium  to  uranium  varying  from  1.82  X  10~7  for  chalcolite 
from  Saxony  to  3.74 XlO~7  for  pitchblende  from  Cornwall;  whereas 
for  two  pitchblendes  from  Norway  she  reported  3.48  X  10~7  and 
3.64  X  10~7,  respectively. 

CONSTANCY   OF   THE   RATIO   IN   PITCHBLENDES. 

The  most  recent  experimental  contribution  to  the  subject  is  the 
searching  examination  by  Heimann  and  Marckwald  «  of  the  radium- 
uranium  ratio  in  eight  samples  of  pitchblende  from  all  the  principal 
pitchblende  localities  of  the  world,  including  Joachimsthal,  Saxony, 

a  Marckwald,  W.,  and  Russell,  A.  S.,  tJber  den  Radiumgehalt  einiger  Uranerze:  Her.  Deutsch.  chem. 
Gesell.,  Jahrg.  44,  Bd.  1, 1911,  pp.  771-775;  Uber  den  Radiumgehalt  von  Uranerzen:  Jahrb.  Radtoakt. 
Elektronik,  Bd.  8,  1911,  p.  457. 

6  Gleditsch,  Ellen,  loc.cit. 

c  Soddy,  Frederic,  and  Pirret,  Ruth,  loc.  cit. 

d  Gleditsch,  Ellen,  Sur  le  rapport  entre  P uranium  et  le  radium  dans  les  mineraux  actlB:  L«  Ki     ium , 

Vnetaann,  Berta,  and  Marckwald,  W.,  Uber  den  Radiumgehalt  von  Pechblenden:  Physlk.  Ztechr., 
Jahrg.  14,  1913,  pp.  303-305;  Jahrb.  Radioakt.  Elektronik,  Bd.  10, 1913,  p.  299. 


8  THE   RADIUM-URANIUM    RATIO   IN   CARNOTITES. 

German  East  Africa,  Norway,  Bohemia,  Colorado,  and  Cornwall. 
Determinations  were  made  by  two  entirely  different  methods — the 
emanation  method  and  the  gamma-ray  method.  For  all  eight  sam- 
ples the  ratio  was  found  to  be  constant  within  0.4  per  cent.  The 
absolute  value  of  the  ratio  was  determined  by  comparison  with  a 
radium  solution  having  its  origin  in  the  Honigschmid0  atomic- 
weight  radium  of  the  Institute  for  Kadium  Eesearch  in  Vienna,  and 
was  found  to  be  3.328  X  10~7.  The  satisfactory  agreement  of  this 
number  with  the  theoretical  value  of  the  ratio  as  calculated  from 
radiation  data  6  lend  it  additional  reliability. 

THE    RATIO    IN    CARNOTITES. 

As  already  stated,  a  few  investigators  have  included  carnotites 
among  the  uranium  minerals  they  examined.  The  results  of  Bolt- 
wood  c  and  of  McCoy d  show  no  abnormally  low  ratio  for  this  mineral. 
Mile.  Gleditsch e  reported  for  a  sample  of  Colorado  carnotite  a  ratio 
of  only  2.34  X  10~7,  which  corresponds  to  about  70  per  cent  of  the 
normal  ratio.  Marckwald  and  Russell -^  found  that  the  ratio  was 
91.6  per  cent  of  normal  ratio  for  a  carnotite  from  Colorado  and  71.5 
per  cent  for  one  from  Florida  (?).^  The  impression  seems  to  have 
been  general,  probably  because  of  these  results,  that  carnotite  always 
has  a  low  ratio. 

By  way  of  anticipation,  the  authors  of  this  paper  state  here  that 
with  small  samples  they  have  sometimes  confirmed  the  low  ratios, 
finding  one  almost  as  low  as  that  found  by  Mile.  Gleditsch,  which, 
however,  is  to  be  regarded  as  exceptional.  On  the  other  hand,  the 
authors  have  also  found  an  equal  number  of  high  ratios  Qikewise 
in  small  samples  only),  some  as  high  as  the  highest  ratios  found  by 
Mile.  Gleditsch  for  any  of  the  primary  minerals  and  one  considerably 
higher,  4.6X10"7,  which  is  the  highest  ratio  yet  reported  for  any 
uranium  mineral. 

What  appears  to  the  authors  to  be  of  the  greatest  significance  is 
the  fact  that  these  abnormal  ratios,  both  high  and  low,  occur  only  in 
samples  representing  small  quantities  (a  few  pounds)  of  ore;  whereas 

a  Honigschmid,  O.,  Revision  des  Atomgewichtes  des  Radiums  und  Herstellung  von  Radiumstandard- 
praparaten:  Sitzb.  K.  Akad.  Wiss.,  Abt.  2-a,  Bd.  120,  1911,  pp.  1617-1652. 

6  See  calculation  by  Meyer,  Stefan,  liber  die  Lebensdauer  von  Uran  und  Radium:  Sitzb.  K.  Akad 
Wiss.,  Abt.  2-a,  Bd.  122,  June,  1913,  p.  1085. 

c  Boltwood,  B.  B.,  On  the  ratio  of  radium  to  uranium  in  some  minerals:  Am.  Jour.  Sci.,  ser.  4,  vol. 
18, 1904,  pp.  97-103;  On  the  radioactivity  of  uranium  minerals:  vol.  25,  1908,  pp.  269-298. 

<J  McCoy,  H.  N.,  Ueber  das  Entstehen  des  Radiums:  Ber.  Deutsch.  chem.  Gesell.,  Jahrg.  37,  Bd.  3, 
1904,  pp.  2641-2656;  Radioactivity  as  an  atomic  property:  Jour.  Am.  Chem.  Soc.,  vol.  27,  pt.  1, 1905,  p. 
391. 

«  Gleditsch,  Ellen,  Sur  le  rapport  entre  1'uranium  et  le  radium  dans  les  mine'raux  actifs:  Le  Radium, 
t.  8, 1911,  pp.  256-273. 

/  Marckwald,  W.,  and  Russell,  A.  S.,  Uber  den  Radiumgehalt  einiger  Uranerze:  Ber.  Deutsch.  chem. 
Gesell.,  Jahrg.  44,  Bd  1,  1911,  p.  771;  tiber  den  Radiumgehalt  von  Uranerzen:  Jahrb.  Radioakt.  Elek- 
tronik,  Bd.  8,  1911,  p.  457. 

e  The  authors  of  this  paper  have  not  been  able  to  verify  the  occurrence  of  carnotite  in  Florida. 


DISCUSSION    OF    METHODS   USED.  9 

all  samples  from  large  lots  (one  ton  to  a  carload)  invariably  show  a 
ratio  practically  identical  with  that  of  pitchblende.  This  relation 
seems  to  suggest  strongly  a  possible  transposition  of  radium  within 
the  ore  body  rather  than  one  of  complete  removal  by  leaching.  The 
point  is  more  fully  discussed  on  a  later  page  (pp.  26-27) ;  but  evidently 
there  is  no  reason  to  suppose  an  abnormal  ratio  in  carnotite  provided 
the  determination  be  made  on  a  sample  representative  of  a  consid- 
erable portion  of  an  ore  body,  whereas  if  the  quantity  of  ore  repre- 
sented by  the  sample  be  small,  the  result  may  be  either  too  high  or 
too  low. 

DESCRIPTION  OF  SAMPLES. 

The  samples  of  carnotite  investigated  were  chosen  with  the  object  of 
their  representing  the  carnotite  of  all  the  principal  localities  in  Col- 
orado and  Utah  where  the  mineral  has  been  found  in  important 
quantities.  All  grades  of  carnotite  containing  1.5  to  33  per  cent  of 
U3O8  have  been  included. 

The  samples  were  not  collected  by  the  authors,  nor  were  they 
taken  with  any  reference  to  geological  conditions  or  position  in  ore 
beds ;  they  simply  represent  carnotites  that  come  on  the  market  either 
as  specimens  or  in  commercial  quantities.  As  already  mentioned, 
a  special  significance  attaches  to  the  specimens  representing  large 
quantities  of  ore.  Owing  to  the  large  output  of  carnotite  ore  hi  1913 
the  authors  fortunately  were  able  to  obtain  "pulp"  samples  repre- 
senting large  quantities  of  carefully  sampled  ore,  which  the  authors 
believe  to  be  of  the  utmost  importance  in  obtaining  the  true  content 
of  radium.  The  samples  analyzed  were  supplied  through  the  cour- 
tesy of  Messrs.  W.  L.  Cummings,  Thomas  F.  V.  Curran,  Gordon 
Kimball,  W.  L.  Meyer,  David  Taylor,  and  the  National  Radium 
Institute. 

DISCUSSION  OF  METHODS  USED. 

Two  distinct  determinations  enter  into  the  radium-uranium  ratio 
which  affect  equally  the  accuracy  of  the  result.  The  measurement 
of  radium  in  carnotite,  as  in  other  ores,  is  most  readily  accomplished 
by  the  emanation  method,  which  consists  in  the  liberation  by  any 
suitable  method  of  the  radium  emanation  corresponding  to  the  radium 
in  the  ore,  the  quantity  of  emanation  and  of  radium  being  ascertained 
by  using  an  electroscope  with  a  gas-tight  ionization  chamber.  The  ema- 
nation method  may  be  employed  after  the  ore  has  been  prepared  by 
either  of  two  methods:  (a)  The  ore  is  kept  in  a  closed  vessel  for  a 
month  or  more  until  it  has  attained  its  maximum  equilibrium  quan- 
tity of  emanation;  or  (&)  the  emanation  is  initially  reduced  to  zero 
and  subsequently  allowed  to  accumulate  in  a  closed  vessel  for  a 
known  period  (usually  several  days),  the  maximum  amount  and 
67885°— 15 2 


10  THE   RADIUM-URANIUM    RATIO   IN    CARNOTITES. 

hence  tne  radium  content  being  then  calculated  by  means  of  the  Kolo- 
wrat  tables.*  Only  the  former  or  "equilibrium"  method  was  em- 
ployed for  final  values  in  the  radium  determinations  reported  in 
this  paper.  Results  obtained  by  the  accumulation  method  are  re- 
ported on  page  17  as  being  unsatisfactory. 

Aluminum  leaf  electroscopes  of  the  Wilson  type,  with  ionization 
chamber  and  leaf  system  separate  were  used.  A  full  description  of 
the  electroscopes  and  the  manipulative  details  will  be  found  on  sub- 
sequent pages.  The  instruments  were  calibrated  by  means  of 
analyzed  pitchblende  from  Colorado,  the  ratio  found  by  Heimann 
and  Marckwald6  of  3.328 XlCT7  being  assumed  to  be  correct. 

The  determination  of  uranium  in  carnotite  presents  especial  diffi- 
culties because  of  the  presence  of  vanadium,  and  many  of  the  earlier 
proposed  methods  of  separating  the  two  metals  have  proved  un- 
suitable. A  full  description  of  the  method  used  by  Ledoux  &  Co., 
which  the  authors  of  this  paper  found  satisfactory,  is  given  on  pages 
21  and  22,  as  well  as  references  to  other  methods  that  were  sometimes 
employed  for  control. 

The  small  quantity  of  uranium  hi  most  carnotites  as  compared 
with  that  in  higher-grade  ores  renders  difficult  the  attaining  of  the 
desired  degree  of  accuracy  in  determining  the  uranium,  and  to  a 
less  degree  the  radium  content.  The  authors  sought  to  overcome 
this  difficulty  by  repeating  determinations  frequently  and  by  employ- 
ing additional  methods  of  control  in  all  cases  of  doubt.  All  radium 
determinations  have  been  checked  by  at  least  two  independent 
methods  of  liberating  the  emanation.  The  average  results  reported 
on  pages  23  to  26  are  believed  to  be  accurate  within  1  to  2  per  cent. 

THE  EMANATING  POWER  OF  CARNOTITE. 

The  term  "emanating  power"  was  first  used  by  Boltwood c  to 
signify  the  percentage  loss  of  emanation  from  a  radioactive  substance, 
and  in  the  determination  of  radium  it  was  applied  by  him  as  an  additive 
correction  to  the  quantity  of  emanation  liberated  by  direct  solution. 
Such  a  correction  is  of  especial  importance  in  determining  radium  in 
carnotites  in  which  the  authors  have  found  the  emanating  power  to 
be  high,  from  16  to  50  per  cent  (see  Table  1).  This  high  emanating 
power,  which  is  one  of  the  distinguishing  characteristics  of  carnotite, 
was  a  controlling  factor  in  the  experimental  procedure,  hence  it  is 
discussed  somewhat  fully  here. 

a  Kolowrat,  Le"on.    Le  Radium,  t.  6, 1909,  p.  194.    Also  given  in  most  treatises  on  radioactivity. 
»  Heimann,  Berta,  and  Markwald,  W.,  Tiber  den  Radiumgehalt  von  Pechblenden:  Physik.  ztschr., 
Jahrg.  14, 1913,  p.  303;  Jahrb.  Radioakt.  Electronik,  Bd.  10, 1913,  p.  299. 

c  Boltwood,  B.  B.,  The  origin  of  radium:  Philos.  Mag.,  vol.  9, 1905,  pp.  599-613. 


THE   EMANATING   POWER  OF   CAENOTITE.  H 

The  loss  of  emanation  by  the  ore  is  due  to  diffusion  of  the  gas  and 
is  much  lower  (only  3  to  8  per  cent)  for  dense,  compact  minerals 
like  pitchblende  than  for  carnotites,  which  have  a  looser  mechanical 
structure.  For  a  given  sample  the  loss  is  doubtless,  as  suggested  by 
Rutherford,0  dependent  on  the  degree  of  fineness  to  which  the  ore 
is  pulverized.  The  authors  of  this  paper  have  not  undertaken  any 
direct  investigation  of  the  relation  between  emanating  power  and 
fineness  or  any  other  property,  but  have  ascertained  that  among 
different  specimens  fineness  can  not  be  the  principal  controlling 
factor,  for  there  seems  to  be  no  relation  whatever  between  the  order 
of  fineness  of  different  samples  and  their  emanating  power. 

Evidently  a  given  percentage  error  in  determining  the  emanating 
power  to  be  used  additively  in  obtaining  the  total  emanation  by 
Boltwood's  method  would  more  seriously  affect  the  final  result  in 
the  case  of  a  carnotite  than  in  that  of  an  ore  for  which  the  relative 
value  of  the  emanating  power  is  small. 

Repetition  by  the  writers  of  this  paper,  of  earlier  determinations  made 
by  them,  showed  considerable  variation  in  emanating  power,  which  sug- 
gested that  the  emanation  was  not  always  removed  to  the  same  degree 
from  the  same  sample.  This  variation  is  probably  caused  by  dif- 
ferences in  the  volume  of  air  passed  over  the  ore,  or  to  differences  in 
pressure  or  velocity  of  the  air,  and  the  consequent  drawing  of  varying 
amounts  of  emanation  out  of  the  more  or  less  porous  structure.  As 
a  remedy  the  authors  used  a  simple  modification  of  the  Boltwood 
method,  namely,  making  the  determination  of  the  emanating  power 
and  the  emanation  liberated  by  solution  strictly  " complementary" 
to  each  other — in  the  sense  that  each  sample  dissolved  should  repre- 
sent part  or  all  of  the  sample  from  which  emanation  had  just  been 
drawn  to  determine  the  emanating  power.  By  this  procedure  it  does 
not  matter  whether  corresponding  determinations  of  emanating 
power  are  concordant  or  not,  so  long  as  the  sums  obtained  by  adding 
corresponding  determinations  are  in  agreement.  That  this  assump- 
tion is  correct  may  be  seen  from  the  following  table,  which  shows  that 
for  each  ore  the  agreement  for  the  total  emanation  is  better  than  that 
of  either  of  the  individual  values  going  to  make  up  the  sum.  Only 
a  few  examples  illustrative  of  this  point  are  given  because  it  was 
found  more  convenient  to  determine  the  total  emanation  in  one 
operation,  as  described  later.  In  this  and  other  tables  each  ore  is 
designated  by  the  same  number  throughout. 

a  Rutherford,  E.  E.,  Radioactive  substances  and  their  radiations,  1913,  p.  364. 


12  THE    RADIUM-UBANIUM    EATIO   IN    CARNOTITES. 

Table  illustrating  advantage  of  "complementary"  emanation  method. 


Total  a 

Emana- 

Solution 

emana- 

Number of  ore. 

ting 
power, 
curiesx 

emana- 
tion, 
curies  X 

tion  per 
gram  of 
ore, 
curieslx 

2  

/    15.0 
\    17.6 

87.1 
84.5 

102.1 
102.1 

4  

/    14.0 

58.6 

72.6 

5 

\    11.7 
/    21.8 

27.7 

49.5 

\    23.6 

26.2 

49.8 

/      4.38 

8.93 

13.3 

(      4.45 

8.50 

13.0 

a  Each  value 
columns. 


this  column  is  the  sum  of  the  two  values,  on  the  same  line,  in  the  two  preceding 


IMPRACTICABILITY  OF  SOLID-ORE  RADIATION  METHOD  FOR  CARNOTITE. 

It  should  also  be  noted  in  discussing  emanating  power  that  the 
high  and  variable  values  exhibited  by  carnotite  seem  to  preclude 
the  possibility  of  employing  for  accurate  determination  any  radiation 
method  from  the  solid  ore  for  either  the  alpha,  the  beta,  or  the 
gamma  rays  unless,  in  the  employment  of  the  gamma-ray  method,  a 
large  quantity  of  ore  could  be  kept  for  a  month,  and  later  measured, 
in  an  absolutely  tight  vessel. 

EMANATION  METHOD  FOB  THE   DETERMINATION  OF  RADIUM. 

For  the  liberation  of  emanation  from  carnotite  the  authors  origi- 
nally planned  to  use  three  methods:  (a)  Solution  method — boiling 
in  1: 1  HNO3  solution;  (6)  fusion  method — fusing  with  a  mixture  of 
and  KjCOg;  (c)  fusion  and  solution  method — fusing  with 
and  K2CO3,  followed  by  solution  in  5  per  cent  Na^COg  solu- 
tion, filtration,  solution  of  the  residue  in  1 :  3  HNO3  solution,  and 
separate  treatment  of  both  solutions.  The  failure  of  methods  &  and 
c  to  give  satisfactory  results  (see  table  on  p.  17)  led  to  the  use  of  a 
fourth,  (d)  ignition  method  without  flux.  A  description  of  the  de- 
tails of  these  methods  is  given  in  the  following  paragraphs. 

SOLUTION    METHOD. 

The  solution  method  may  be  used  as  described  (p.  11)  by  adding  the 
"emanating  power"  to  the  "solution  emanation."  In  this  procedure 
the  authors  found  it  advisable  to  modify  the  Boltwood  method  by 
making  the  two  determinations,  complementary  to  each  other,  as 
already  stated. 

SOLUTION    EMANATION   METHOD   IN   A   SINGLE    OPERATION. 

Unless  one  desires  to  know  the  emanating  power  itself  it  is  simpler 
to  determine  the  total  emanation  in  one  operation  by  sealing  the  ore 
hi  a  very  thin  bulb,  of  the  type  shown  in  figure  1,  for  a  month  or 
more  before  breaking  under  acid  to  liberate  the  total  emanation. 


fTO  GAS 
1  BURETTE 


EMANATION   METHOD  FOR  DETERMINATION  OF  RADIUM.  13 

The  bulb  a,  of  4  to  10  mm.  diameter,  according  to  the  quantity  of 
ore  to  be  used,  is  blown  very  thin  so  as  to  break  without  endangering 
the  outer  flask  /,  contain- 
ing .HNO3.  The  ore  is 
weighed  into  the  bulb 
through  I  and  then  the 
glass  stem  c  is  sealed  on 
and  is  constricted  to  make 
a  complete  seal  at  d,  the 
upper  end  e  being  also 
sealed  for  convenience. 
The  whole  is  introduced 


through  a  double  -  bored 
rubber  stopper  to  a  point 
just  off  the  bottom  of  the 
flask  /  and  may  be  broken 
by  a  slight  downward  rap 
on  e.  By  boiling  the  acid, 
the  ore  is  -readily  attacked 
and  all  of  the  emanation 
is  boiled  over  into  a  gas 
burette  (see  fig.  2). 

The  results  obtained  with  this  method  check  excellently  with  the 
results  of  the  "complementary"  modified  Boltwood  method  as  can 
be  seen  from  the  following  table: 

Results  of  sealed  bulb  method  for  total  emanation  in  one  operation,  compared  with  com- 
plementary method. 


CARNOTITE 


FIQTJBE  1.— Apparatus  for  determining  emanation  by  sealed- 
tube  method. 


Number 
of  ore. 

Method  used. 

Emanating 
power, 
curiesX10». 

Solution 
emanation, 
ciiriesXlO". 

Total  ema- 
nation per 
gram  of  ore, 
curiesXlO*. 

[Sealed  bulb  

11.09 

\Complementary  

/  Sealed  bulb 

3.906 

7.188 

11.09 
8.08 

\Complementafy  
/Sealed  bulb 

3.488 

4.467 

"7.96 
7  08 

16  

3.191 

3.916 

o7.ll 

/Sealed  bulb 

7.34 

18  

1.224 

6.156 

o7.38 

/Sealed  bulb 

a  54 

\Complementary  

2.993 

5.606 

08.60 

/Sealed  bulb 

29.91 

20  

9.847 

19.77 

a29.62 

/Sealed  bulb                                                          

23.61 

21  

10.72 

13.12 

•*« 

/Sealed  bulb 

21.21 

22  

3.445 

17.64 

021.09 

P               7 

i  Sum  of  results  given,  on  same  line,  in  the  two  preceding  columns. 


14 


THE    RADIUM-URANIUM    RATIO   IN    CARNOTITES. 


k 


SOLUTION   AND    BOILING   OFF    EMANATION. 

The  method  of  solution  and  boiling  off  the  emanation  requires  no 
especial  explanation.  The  apparatus  is  shown  in  figure  2. 

Hot  water  containing  some  NaOH  is  used  in  the  gas  burette  Tc; 
1 :1  HNO3  solution  is  used  as  a  solvent  of  the  carnotite.  A  glass  stop- 
cock at  s  is  more  convenient  than  rubber  tubing  and  a  clamp.  All 
possibility  of  loss  of  emanation  by  the  passage  of  water  into  the  side 
arm  t  is  avoided  by  allowing  all  air  to  pass  up  into  Tc  before  the  bulb  a 
is  broken.  In  case  an  ore  is  not  sealed  in  glass,  the  same  result  may 
be  accomplished  by  placing  the  ore  in  a 
filter  paper  and  folding  the  paper  so  that 
it  remains  in  the  neck  of  the  flask  /  until 
all  air  is  expelled  and  the  steam  softens 
the  paper,  allowing  it  and  its  contents  to 
drop  into  the  acid.  The  stopcock  should 
be  closed  at  this  time  (or  on  breaking  the 
glass  bulb)  and  then  gradually  opened  to 
prevent  a  sudden  rush  of  gas  from  carry- 
ing undissolved  ore  up  into  the  alkaline 
solution. 

Pitchblende  used  for  standardization 
purposes  was  treated  in  the  same  way  as 
carnotite,  either  directly  with  correction 
for  emanating  power,  or  from  a  glass  tube 
that  had  been  sealed  for  one  month. 

FUSION   METHOD. 

The  great  advantage  of  ' '  accumulation  " 
over  "equilibrium"  emanation  methods 
requiring  a  month,  led  the  authors  to 
attempt  to  employ  a  fusion  method,  since 
accumulation  in  solution  is  well  known  to 
give  low  results  because  of  the  removal  of 
radium  by  precipitation  or  by  adsorption.  The  method  employed  is 
as  follows: 

'A  quantity  of  ore  sufficient  to  furnish  enough  emanation  to  produce 
a  discharge  of  about  one  scale  division  per  second,  is  thoroughly  fused 
over  a  Meker  burner  in  a  platinum  boat  or  dish  with  five  or  more 
times  its  weight  of  a  mixture  of  one  part  Na2CO3  to  one  part  K2CO3, 
enough  tune  being  allowed  during  fusion  for  all  emanation  to  be 
driven  off  from  the  fused  mass.  The  tune  of  solidification  is  noted 
as  the  zero  point  for  the  accumulation  of  emanation  and  the  fusion 
is  set  aside  in  a  desiccator  for  three  or  four  days;  it  is  not  necessary 
to  keep  the  fused  mass  in  a  sealed  vessel  during  accumulation,  as  a 
special  experiment  showed  that  there  is  no  emanation  loss  from  the 


FIGURE  2.— Apparatus  for  dissolving 
carnotite  and  collecting  the  emana- 
tion. 


EMANATION   METHOD  FOR  DETERMINATION   OF  RADIUM.  15 

cold  fusion.  The  second  fusion  to  liberate  emanation  may  be  made 
either  in  the  platinum  boat  in  which  the  first  was  made  by  inserting 
the  boat  into  a  silica  tube  with  ground  glass  joints  as  proposed  by 
Ebler,a  or  better  still,  to  attain  a  higher  temperature  the  fusion  is 
removed  from  the  boat  or  dish  and  inserted  into  Jena  combustion 
tubing  of  suitable  diameter,  in  which  it  is  held  in  place  by  glass  wool 
plugs  that,  reacting  with  the  flux,  furnish  a  vigorous  evolution  of  car- 
bon dioxide  to  assist  in  the  removal  of  emanation.  The  heating  is 
accomplished  by  means  of  a  Meker  burner  and  is  continued  until  the 
Jena  glass  completely  collapses.  A  higher  temperature  is  obtained 
in  the  bare  Jena  glass  than  in  a  platinum  boat  inside  a  silica  tube, 
but  on  the  other  hand  one  loses  the  advantage  of  being  able  to  repeat 
the  fusion  any  number  of  tunes  after  renewed  accumulation. 

In  spite  of  its  great  promise  and  actual  success  hi  experiments  with 
pitchblende  and  crude  sulphates,  the  fusion  method  has  proved  a 
failure  for  carnotite,  even  for  high-grade  ore  requiring  only  a  small 
quantity  of  flux,  as  will  be  seen  in  the  table  on  page  17.  If  a 
higher  temperature,  by  electric  heating,  were  used  the  method 
might  yield  correct  results,  but  such  heating  was  not  tried  because 
of  the  same  end  being  attained  more  readily  by  the  method  of  igni- 
tion without  flux.  Two  general  precautions  should  be  mentioned 
here:  (1)  The  gases,  should  be  allowed  to  stand  in  a  gas  burette  for 
about  10  minutes  to  permit  the  decay  of  thorium  emanation  before 
they  pass  into  the  emanation  chamber.  As  no  evidence  has 
been  obtained  of  the  presence  of  thorium  in  carnotite  this  precaution 
may  be  omitted.  (2)  In  case  of  a  large  evolution  of  carbon  dioxide 
from  the  fusion  in  glass,  a  potash  bulb  should  be  inserted  in  front  of 
the  drying  bulb  to  prevent  carbon  dioxide  from  entering  the  ioniza- 
tion  chamber;  otherwise,  the  fact  that  the  "specific  ionization"  of 
carbon  dioxide  is  greater  than  that  of  air  makes  the  results  obtained 
too  high. 

FUSION-AND-SOLUTION  METHOD. 

Fuse  the  ore  with  a  mixture  of  Na2CO3  and  K2CO8  as  described 
for  the  fusion  method,  dissolve  in  a  5  per  cent  Na-jCOg  solution,  filter, 
dissolve  the  residue  in  1 : 3  HNO3  solution,  and  remove  the  emanation 
from  both  the  acid  and  alkaline  solutions  by  passage  of  air  for  at 
least  10  minutes.  Place  each  solution  in  a  Jena  flask  and  seal  with 
a  rubber  stopper  fitted  with  a  glass  tube  having  the  upper  end  drawn 
out  to  a  capillary  point.  After  an  accumulation  period  of  several 
days  the  glass  tube  is  connected  with  the  collector  by  a  piece  of 
rubber  tubing,  and  the  point  of  the  glass  tube  is  broken  inside  the 
rubber  tubing  before  boiling  off  the  emanation,  as  described  for  solu- 
tion method.  

a  Ebler,  Erich,    ttber  die  Bestimmung  dos  Radiums  in  Mineralien  und  Gestelnen:  Ztachr.  Elektro- 
chem.,  Bd.  18,  1912,  p.  532. 


16  THE   RADIUM-URANIUM   RATIO  IN   CARNOTITES. 

As  shown  by  the  table  on  page  17,  the  fusion-and-solution  method 
gives  results  10  to  20  per  cent  low,  doubtless  because  of  the  adsorp- 
tion of  radium  or  radium  emanation  in  the  colloidal  silica  which  almost 
invariably  appears  in  the  carbonate  and  sometimes  in  the  acid  solution 
also,  even  after  refiltering  once  or  twice.  The  method  appears  to 
give  better  results  with  substances  containing  little  or  no  silica,  but 
for  those  the  simple  direct-fusion  method  is  also  applicable.  The 
carbonate  solution  usually  filters  very  slowly,  and  on  the  whole  the 
authors  do  not  recommend  the  fusion-and  solution  method  as  being 
either  accurate  or  convenient  for  carnotites. 

IGNITION    METHOD. 

The  application  of  the  ignition  method  to  carnQtite  was  suggested 
by  the  ease  with  which  the  ore  itself  liberates  its  emanation  even  in 
the  cold,  whereas  the  cold  fusion  loses  none. 
Should  such  a  difference  persist  at  higher  tem- 
peratures, ignition  without  flux  would  appear 
preferable.  In  fact,  this  method  has  been  found 
entirely  satisfactory. 

To  hold  the  ore,  straight  pieces  of  Jena  combus- 
tion tubing,  about  4  to  10  mm.  internal  diameter, 
depending  on  the  volume  of  the  sample,  and  about 
15  to  20  cm.  long,  were  used.  One  end  of  a  tube 
was  drawn  to  a  point  and  the  weighed  ore  was 
introduced  through  the  open  end,  which  was  then 
drawn  out  and  sealed.  Glass  wool  plugs  were  used 
to  hold  the  ore  in  place  in  the  middle  of  the  tube. 
After  standing  one  month  or  more  the  tube  was 
connected  by  means  of  sulphuric-acid  microdrying 
bulbs  (fig.  3)  to  the  exhausted  electroscope  on  one 
FIGUBE  3  —sulphuric-  s^e  an(^  ^°  ^ne  outside  air  on  the  other  side.  After 
acid  microdrying  buib.  the  capillary  ends  inside  the  rubber  connections 
were  broken  air  was  allowed  to  pass  over  the  ore  into  the  electroscope, 
the  tube  being  heated  over  a  Meker  burner  1J  inches  in  diameter 
until  the  Jena  glass  completely  collapsed.  This  treatment,  as  the 
following  table  shows,  gives  complete  de-emanation. 

Air  was  passed  directly  over  the  ore  through  a  drying  bulb  into  the 
electroscope — a  procedure  that  is  justified  only  when  thorium  is  ab- 
sent. That  the  ore  contained  no  thorium  is  supported  by  two  experi- 
mental observations — first,  that  the  electroscope,  after  the  radium 
emanation  is  pumped  out,  returns  in  a  few  hours  to  its  normal  natural 
leak,  whereas  it  would  not  do  so  if  contaminated  by  active  deposit  of 
thorium  emanation;  and,  second,  the  results  obtained  by  the  ignition 
method  agree  well  with  those  obtained  by  the  solution  method,  in 


ELECTEOSCOPIC   DETERMINATION   OP  RADIUM. 


17 


which  the  emanation  was  always  permitted  to  stand  in  a  gas  burette 
for  10  minutes  before  being  passed  into  the  emanation  chamber.  It 
seems  certain,  then,  that  there  is  little  or  no  thorium  in  carnotites. 
In  the  following  table  is  a  comparison  of  results  obtained  for  a 
number  of  carnotite  ores  by  using  the  four  methods  just  described. 
Examination  of  these  results  shows  that  the  solution  method  and  the 
ignition  method  give  concordant  results,  whereas  the  fusion  method 
and  the  fusion-and-solution  method  give  low  results.  For  this  reason 
the  two  latter  methods  were  not  employed  in  obtaining  any  of  the 
data  reported  in  Table  I. 

Comparison  of  results  of  different  methods  for  de-emanating  carnotites. 


Number 
of  ore. 

Total  emanation  in  curies  X  10»  by  method  of— 

Solution  in 
1:1HNO8. 

Fusion 
with 
NauCOa 
andKjCO8. 

Ignition. 

Fusion 
and 
solution. 

2  

4 

101.4 
72.6 
7.83 
11.09 
8.08 
7.11 
8.66 

63.5 

98.0 
73.3 
7.89 
11.63 

83.0 
53.8 
6.20 
8.92 
6.98 

13  

2.62 

14  
15  

16  
17  

7.17 
8.65 

7.38 

ELECTROSCOPIC  DETERMINATION  OP  RADIUM. 

Two  electroscopes  were  employed  in  making  determinations,  both 
being  of  the  Wilson  type,  with  sulphur  insulation  in  the  neck  sepa- 
rating the  ionization  chamber  from  the  leaf  system.  One  of  the 
electroscopes  a  had  a  chamber  of  1  liter  capacity.  The  other  electro- 
scope differed  only  in  having  a  cylindrical  ionization  chamber  of 
about  i-Hter  capacity. 

This  type  of  instrument  has  several  advantages  over  that  with  the 
leaf  system  contained  in  the  ionization  chamber.  The  charging 
device  is  simpler  and  can  always  be  brought  back  to  a  definite 
position,  thus  avoiding  the  danger  of  a  variable  electrical  capacity. 
A  charge  can  also  be  easily  maintained  for  any  desired  time  during  the 
formation  of  induced  activity,  something  that  can  not  be  conveniently 
done  with  instruments  having  a  suspended  charging  rod  controlled  by 
a  magnet. 

ELECTROSCOPE   WITH  DETACHABLE   IONIZATION   CHAMBER. 

A  new  type  of  electroscope  has  recently  been  devised  by  one  of 
the  authors  to  facilitate  making  a  large  number  of  radium  deter- 
minations daily  at  a  minimum  expense  for  instruments. 

«  For  a  description  and  view  of  this  electroscope  see  Moore,  R.  B.,  and  Kithil,  K.  L.,  A  preliminary 
report  on  uranium,  radium,  and  vanadium:  Bull.  70,  Bureau  of  Mines,  1914,  p.  66. 


18 


THE  RADIUM-URANIUM   RATIO  IN   CARNOTITES. 


The  new  electroscope  (fig.  4  and  PI.  I,  A  and  B)  has  an  ionization 
chamber  a  (fig.  4),  detachable  from  an  upper  cage  6,  containing  the 
leaf  system  and  microscope.  By  this  device  any  number  of  ioniza- 
tion chambers  may  be  used  with  one  electroscope,  thus  avoiding 
duplication  of  the  more  expensive  and  delicate  parts  of  the  instru- 
ment. The  advantages  are  obvious  if  one  considers  that  in  an  ordi- 
nary emanation  electroscope  only  one  determination  can  be  made 
daily,  whereas  in  the  detachable  form  as  many  may  be  made  as  one 
has  ionization  chambers.  An  ionization  chamber  costs  about  one- 
tenth  as  much  as  the  complete  instrument,  hence  an  equipment 

equivalent  in  use  to  10  electroscopes 
may  be  had  for  the  cost  of  two. 

The  ionization  chamber  may  be  of 
any  form  or  size.  For  emanation 
determinations  a  cylinder  of  the  type 
shown  in  figure  4  is  recommended. 
A  cylindrical  electrode  e  is  insulated 
from  the  chamber  by  means  of  the 
best  quality  of  "bankers' "  or  " spe- 
cie" sealing  wax  d,  which  also  serves 
to  make  the  vessel  gas  tight.  The 
sealing  wax  is  set  in  a  brass  collar 
that  screws  into  the  top  of  the  ioni- 
zation chamber  onto  a  lead  washer 
and  can  be  readily  removed  when 
one  desires  to  renew  the  insulation 
or  examine  its  tightness.  The  elec- 
trode terminates  outside  the  cham- 
ber in  a  small  conical  brass  tip  c, 
serving  to  make  electrical  contact 
with  a  spring  s.  When  the  upper 
part  of  the  instrument  is  removed  it 
is  replaced  with  a  friction  cap  of 
brass  (PI.  I,  B)  to  protect  the  electrode  tip  and  sealing  wax  insula- 
tion from  contamination.  To  the  brass  outlet  tubes  o  o  (fig.  4) 
glass  stopcocks  are  attached  by  means  of  heavy  rubber  tubing 
securely  wired  on  to  insure  a  gas-tight  joint.  In  all  other  respects  the 
ionization  chamber  is  similar  to  the  older  forms. 

The  upper  part  of  the  instrument  consists  of  a  cage  6  (fig.  4),  of 
the  usual  form,  housing  the  leaf  system  and,  in  this  case,  also  acting 
as  a  support  for  the  microscope.  The  leaf  system/ is  suspended  from 
the  top  of  the  cage  instead  of  projecting  up  from  the  bottom.  The 
rod  to  which  the  leaf  is  attached  is  set  by  means  of  sealing  wax 
insulation  into  a  brass  cap  g,  which  screws  into  the  top  of  the  cage 
from  the  outside  and  can  be  readily  removed  for  the  replacement  of  the 


FIGURE  4.— Cross  section  of  electroscope  with 
detachable  ionization  chamber  (one- third  size) . 


BUREAU    OF   MINES 


TECHNICAL    PAPER   88      PLATE   I 


A.  ELECTROSCOPE  WITH  INTERCHANGEABLE  IONIZA- 
TION  CHAMBERS.  THE  ELECTRIC-LIGHT  SOCKET  AND 
WIRE  ABOVE  THE  INSTRUMENT  ARE  NOT  PART  OF  IT. 


IONIZATION     CHAMBER    DETACHED    FROM    INSTRU- 
MENT AND  CAP  IN  PLACE. 


ELECTROSCOPIC    DETERMINATION   OF   RADIUM.  19 

aluminum  leaf.  If  the  cap  shows  any  tendency  to  change  position 
it  should  be  set  with  a  drop  of  solder  to  prevent  disturbance  of  the 
calibration.  At  the  bottom  of  the  leaf  support  is  a  light  brass 
spring  s,  serving  to  make  electrical  contact  with  the  conical  point  c 
of  the  electrode  of  the  ionization  chamber.  The  spring  should  press 
lightly  against  the  tip,  enough  to  insure  firm  contact,  but  not  so  hard 
as  to  displace  the  leaf  system  from  its  normal  position  when  the  cage 
&  is  set  down  £>n  the  ionization  chamber  a. 

One  of  the  advantages  of  this  electroscope  is  that  the  microscope, 
being  attached  directly  and  firmly  to  the  leaf  chamber  (see  PI.  I,  A), 
can  not  become  displaced  relative  to  the  leaf.  The  miscroscope  is 
held  in  position  by  a  heavy  brass  collar  set  in  a  vertical  plate  which 
is  parallel  to  the  front  of  the  leaf  chamber  and  is  supported  at  a  dis- 
tance of  about  1  inch  from  it  by  three  supports  screwed  into  the 
outside  of  the  cage  &  (fig.  4). 

The  charging  device  fc,  of  a  simple  and  efficient  type,  is  insulated 
from  the  cage  by  an  ebonite  plug  n,  which  screws  into  the  wall  of 
the  cage.  The  core  of  the  plug  is  also  threaded  to  accommodate 
the  charging  rod  and  to  hold  it  firmly. 

Other  types  of  discharge  chambers  besides  that  for  emanation 
may  be  employed,  for  example,  an  open  chamber  for  solids,  such  as  is 
used  in  the  cursory  examination  of  radioactive  ores,  or  a  large  water 
chamber  of  the  fontactometer  type  as  used  in  determining  the  radio- 
activity of  waters. 

The  purpose  in  designing  this  electroscope  was  to  furnish  a  simple 
and  inexpensive  type  of  instrument,  all  the  parts  of  which,  except  the 
microscope,  can  be  made  by  any  instrument  maker  or  good  mechanic. 
The  design  also  permits  of  the  replacement  of  any  part  without  dis- 
turbing the  rest  of  the  electroscope.  A  detailed  description  of  the 
instrument  will  be  found  in  the  May,  1915,  issue  of  the  Journal  of 
Industrial  and  Engineering  Chemistry. 

STANDARDIZATION   OF   ELECTROSCOPES. 

Standardization  of  electroscopes  was  carried  out  by  dissolving  about 
40  milligrams  of  carefully  analyzed  pitchblende  (see  ore  No.  12,  p.  24) 
from  Colorado  in  boiling  1 : 1  HNO3  solution  according  to  the  procedure 
described  for  carnotites  on  page  14.  The  radium  content  was 
assumed  to  be  that  corresponding  to  Heimann  and  Marckwald's  ° 
ratio  of  3.328  XlCT7.  The  pitchblende  was  analyzed  by  the  method 
given  for  carnotite  on  page  21,  omitting  the  procedure  for  the  separa- 
tion of  vanadium.  A  number  of  shorter  methods  for  determining 
uranium  in  pitchblende  were  found  unreliable. 

a  Heimann,  Berta,  and  Marckwald,  W.,  Uber  den  Radiumgehalt  von  Pechblenden:  Jahrb.  Radioakt 
Electronik,  Bd.  10, 1913,  p.  299;  Physik.  Ztschr.,  Bd.  14,  1913,  p.  303. 


20  THE   RADIUM-URANIUM    RATIO   IN    CARNOTITES. 

DATA   FOR   STANDARD  PITCHBLENDE. 

One  gram  of  standard  pitchblende  contains  0.765  gram  U3O8  or 
0.649  gram  U,  and  2.16X10"7  gram  of  radium.  The  emanating 
power  is  2.7  per  cent.  Therefore,  1  milligram  dissolved  directly  gives 
2.10X"10  curies  of  radium  emanation. 

CONTROL   OF   STANDARDIZATION. 

A  convenient  and  time-saving  procedure  for  control  of  the  stand- 
ardization of  electroscopes,  after  careful  determinations  and  checking, 
was  to  measure  the  discharge  produced  by  the  penetrating  radiation 
from  about  1  milligram  of  radium,  the  element  being  in  the  form  of 
bromide,  in  a  small  sealed  glass  tube.  Another  glass  tube,  large  enough 
to  accommodate  the  radium  tube,  was  fixed  in  a  vertical  position  in 
the  wooden  base  of  the  electroscope  at  a  distance  such  as  to  produce 
a  discharge  at  the  rate  of  about  1  division  per  second.  This  measure- 
ment was  repeated  every  day,  as  was  measurement  of  natural  leak, 
before  using  the  instrument.  For  variations  of  a  few  per  cent 
attributable  to  fluctuations  of  temperature  and  atmospheric  pressure, 
a  correction  was  made.  Greater  variations  were  ascribed  to  changes 
in  the  leaf  system  necessitating  recalibration,  but  recalibrating  was 
not  found  necessary  oftener  than  once  in  one  to  two  months. 

PROCEDURE    IN   USING   THE    ELECTROSCOPE. 

After  the  natural  leak  had  been  determined  and  also  the  pene- 
trating ray  discharge  as  control  of  the  calibration,  the  electroscope  was 
evacuated  to  the  desired  degree,  as  determined  by  a  mercury  manome- 
ter attached  to  one  of  the  stopcocks.  After  such  evacuation  either 
with  an  aspirator  or  a  hand  pump,  the  manometer  was  left  connected 
with  the  electroscope  for  a  few  minutes  to  make  sure  that  the  electro- 
scope was  air-tight.  A  microdrying  tube  was  then  connected  to  one 
stopcock  and  the  air  containing  emanation  passed  into  the  ionization 
chamber  from  the  gas  burette,  the  ignition  tube,  or  the  ' '  emanating 
tube,"  as  the  case  might  be. 

After  standing  about  three  hours  the  instrument  was  charged  for 
about  10  to  15  minutes  to  the  voltage  used  during  measurement. 
It  appeared  to  make  little  difference,  probably  because  of  the  sym- 
metrical form  of  the  ionization  chambers,  whether  induced  activity 
was  allowed  to  accumulate  during  the  whole  three  hours  in  a  chamber 
with  or  without  charge.  Therefore,  the  authors  employed  the  method 
of  charging  for  a  short  time  immediately  before  measurement.  Ten 
duplicate  measurements  were  then  made  over  a  range  of  40  scale 
divisions,  from  which  the  average  rate  of  discharge  was  determined 
before  correcting  for  the  natural  leak.  The  corrected  rate  of  discharge 


THE   DETERMINATION    OF   URANIUM.  21 

can  be  readily  computed  into  terms  of  grams  of  radium  by  means  of 
a  standardization  with  pitchblende  carried  out  in  exactly  the  same 
manner  as  the  measurement  of  the  unknown  sample  of  carnotite. 

THE  DETERMINATION  OP  URANIUM. 

The  method  which  proved  most  satisfactory  for  the  determination 
of  uranium  in  carnotite  is  the  gravimetric  one  of  Ledoux  &  Co., 
described  by  Moore  and  Kithil  a  and  given  below  in  full  detail,  includ- 
ing the  volumetric  determination  of  vanadium. 

GRAVIMETRIC   METHOD  FOR   VANADIUM   AND  URANIUM   IN   CARNOTITE. 

Treat  from  2  to  5  grams  of  ore,  according  to  the  proportion  of  vanadium,  iron, 
and  uranium  present,  in  a  covered  beaker,  with  10  c.  c.  of  HC1  and  let  it  stand  15 
minutes,  shaking  it  occasionally.  Add  5  c.  c.  of  HNO3  and  heat  on  a  steam  bath. 
When  quiet  remove  the  cover  and  evaporate  to  dryness.  Add  3  c.  c.  of  HC1  and  5 
c.  c.  of  water  to  the  residue  and  let  it  stand  on  the  steam  bath  for  a  few  minutes,  stirring 
occasionally.  Dilute  with  25  c.  c.  of  hot  water,  filter  into  a  small  beaker,  and  wash  the 
residue  with  warm  water. 

Some  ores  do  not  yield  all  the  vanadium  to  this  treatment;  a  little  of  it  may  remain 
with  the  insoluble  residue.  To  make  sure  that  all  vanadium  is  in  solution,  ignite  the 
residue  in  a  platinum  dish,  treat  it  with  5  c.  c.  of  HF  and  evaporate  to  dryness  on  a 
steam  bath.  Do  not  bake  the  residue.  It  is  not  necessary  to  expel  all  SiO2.  Add 
3  c.  c.  of  HC1  to  the  residue  from  the  HF  treatment,  and  evaporate  to  dryness.  Repeat 
this  treatment  to  insure  expulsion  of  HF.  Treat  residue  with  2  c.  c.  of  HC1  and  2 
c.  c.  of  water  and  manipulate  until  any  red  crust  is  dissolved,  then  dilute  the  solution 
with  water  and  filter  it  into  the  main  liquid. 

Pass  H2S  into  the  liquid  to  separate  copper,  lead,  and  other  metals  of  this  group, 
filter  and  boil  the  liquid  to  expel  the  H2S.  Concentrate  the  liquid  to  100  c.  c.,  if  nec- 
essary, and  oxidize  it  with  an  excess  of  H202  and  then  neutralize  with  dry  Na-jCC^, 
adding  2  or  3  grams  in  excess.  Boil  the  liquid  for  about  15  minutes  until  the  yellowish 
uranium  precipitate  dissolves,  leaving  a  brown  precipitate  which  is  principally  iron. 
Filter  and  wash  the  iron  precipitate  with  water,  reserving  the  filtrate.  Dissolve  the 
iron  precipitate  in  the  least  possible  amount  of  HN03  (1:1)  and  add  10  c.  c.  of  H20a, 
neutralize  with  Na^CC^,  add  an  excess  of  2  grams  of  Na^COj,  and  boil  as  before.  Filter 
into  the  beaker  containing  the  first  filtrate.  The  iron  precipitate  may  contain  a  little 
vanadium — reserve  it  for  further  treatment. 

Evaporate  the  united  filtrates  from  the  iron  precipitation  to  a  volume  of  about  200 
c.  c.,  add  10  c.  c.  of  strong  HNO3  and  boil  until  all  C02  is  expelled.  Neutralize  the 
free  acid  with  ammonia  (until  a  slight  permanent  precipitate  appears),  then  add  4 
c.  c.  of  HNO3  for  each  100  c.  c.  of  liquid.  Now  add  10  c.  c.  of  a  20  per  cent  lead  acetate 
solution,  and  [enough  (about  20  c.  c.)  of  a  strong  solution  of  ammonium  acetate  to 
reduce  the  hydrogen  ion  concentration  approximately  to  that  of  acetic  acid.]  The 
object  is  to  precipitate  the  vanadium  as  lead  vanadate  in  an  acetic  acid  solution. 
The  ammonium  acetate  solution  may  be  made  by  mixing  80  c.  c.  of  strong  ammonia, 
100  c.  c.  of  water,  and  70  c.  c.  of  acetic  acid  99  per  cent  pure. 

Heat  the  liquid  containing  the  lead-vanadate  precipitate  on  the  steam  bath  for  one 
hour  or  more,  filter  on  a  tight  filter,  and  wash  with  warm  water.  Dissolve  the  pre- 
cipitate in  the  least  possible  quantity  of  hot,  dilute  [not  stronger  than  1:5]  nitric  acid, 

a  Moore,  R.  B.,  and  Kithil,  K.  L.,  A  preliminary  report  on  uranium,  radium,  and  vanadium:  BulL  70^ 
Bureau  of  Mines,  1913,  pp.  88-90. 


22  THE  KADIUM-URANIUM   EATIO  IN   CARNOTITES. 

neutralize  as  before,  add  3  c.  c.  of  HNO3  in  excess,  add  2  c.  c.  of  lead  acetate  solution, 
and  repeat  the  precipitation  of  lead  vanadate  by  adding  ammonium  acetate  in  excess, 
filter  and  add  the  filtrate  to  the  one  from  the  first  precipitation  of  lead  vanadate. 
Reserve  the  precipitate  of  lead  vanadate  for  treatment  as  described  below.  Evaporate 
the  united  filtrates  from  the  lead  vanadate  to  about  400  c.  c.,  add  10  c.  c.  of  strong 
H2S04  to  separate  the  bulk  of  the  lead  (derived  from  the  excess  of  lead  acetate)  as 
PbS04,  filter,  and  wash  the  precipitate  with  cold  water.  Neutralize  the  filtrate  from 
the  PbSO4  with  ammonia  and  add  freshly  prepared  (NH4)HS  until  the  solution  is 
yellow  and  the  uranium  and  what  little  lead  is  present  are  precipitated  as  sulphides. 
Warm  the  mixture  on  a  steam  bath  until  the  sulphides  settle  well.  Filter  and  wash 
slightly  with  warm  water. 

Dissolve  the  precipitate  in  a  No.  2  beaker  with  hot  dilute  (1:2)  HNO3,  add  5  c.  c. 
of  H2S04  and  evaporate  till  fumes  of  H2SO4  appear,  cool  and  take  up  with  water,  boil, 
and  let  the  small  precipitate  of  PbS04  settle  until  the  solution  is  cold;  filter,  and  wash 
the  precipitate  with  [a  little  very]  dilute  H2SO4. 

SEPARATION   OP  ALUMINA. 

Nearly  neutralize  the  filtrate  with  ammonia;  have  the  solutions  cool  (not  warmer 
than  30°  C.),  and  add  powdered  carbonate  of  ammonia  in  about  2  grams  excess  to 
precipitate  the  aluminum,  let  the  precipitate  settle,  filter,  and  wash  with  warm  water. 
If  the  precipitate  is  bulky  or  is  at  all  yellow,  dissolve  it  in  a  little  dilute  H2SO4  and 
reprecipitate  with  ammonium  carbonate  as  described  above.  Acidulate  the  filtrate 
from  the  alumina  with  H2SO4  and  boil  thoroughly  to  expel  CO^  Make  the  liquid 
slightly  alkaline  with  NH4OH  while  it  is  hot,  and  heat  on  the  water  bath  until  the 
ammonium  uranate  collects  and  settles.  Filter  and  wash  with  very  dilute  (2  per 
cent)  solution  of  NH4NO3.  Do  not  allow  the  precipitate  to  run  dry  on  the  filter  after 
the  first  washing.  Dry  the  precipitate,  ignite  it  in  a  porcelain  crucible,  and  weigh 
as  U3O8.  Dissolve  the  precipitate  in  HNO3  and  test  it  with  H2O2  for  vanadium  and 
with  (NH4)2CO3  for  aluminum. 

Dissolve  the  lead  vanadate  in  dilute  HNO3,  add  10  c.  c.  of  H2S04,  and  evaporate  the 
mixture  to  fumes.  Cool,  take  up  with  water  [add  fusion  solution],  add  10  c.  c.  of  a 
concentrated  solution  of  S02  to  the  mixture,  boil  until  the  excess  of  S02  is  expelled 
and  titrate  the  hot  solution  with  a  standard  solution  of  potassium  permanganate. 
The  S02  reduces  the  vanadium  in  solution  from  V205  to  V204.  It  is  not  necessary  to 
filter  out  the  lead  sulphate  before  boiling  to  expel  S02.  The  boiling  is  best  done  in  a 
large  flask.  In  expelling  the  excess  of  SO2  it  is  necessary  to  boil  the  liquid  for  at  least 
10  minutes  after  the  smell  of  SO2  can  no  longer  be  detected. 

The  iron  precipitate  that  was  produced  by  the  addition  of  Na2C03  and  H202  to  the 
original  acid  solution  may  contain  vanadium.  Ignite  the  precipitate  in  a  platinum 
crucible  and  fuse  the  residue  with  Na2CO3,  leach  the  fusion  with  water,  filter,  and 
acidulate  the  filtrate  with  H2S04.  The  filtrate  may  be  addded  to  the  main  solution 
before  reducing  with  S02,  or  reduced  and  titrated  separately,  as  preferred. 

For  the  details  of  other  methods  of  control  the  reader  is  referred  to 
Bulletin  70  °. 

In  general  it  may  be  stated  that  the  most  prevalent  errors  in  the 
determination  of  uranium  result  in  the  precipitation  of  some  other 
oxide,  such  as  SiO2,  A12O3,  or  V2O3,  along  with  uranium,  which  would 
produce  a  low  radium-uranium  ratio.  To  guard  against  errors  from 
the  presence  of  SiO2  or  A12O3,  the  authors  usually  redissolved  the  U3O8 

a  Moore,  R.  B.,  and  Kithil,  K.  L.,  A  preliminary  report  on  uranium,  radium,  and  vanadium:  Bull.  70, 
Bureau  of  Mines,  1914,  pp.  82-91. 


RESULTS   OF   EXPERIMENTS.  23 

precipitate,  passed  the  solution  through  a  Jones's  reductor,  and 
determined  the  uranium  volumetrically  by  titration  with  KMnO4 
solution. 

RESULTS  OF  EXPERIMENTS. 

The  principal  data  in  regard  to  the  samples  tested  and  the  results 
obtained  are  given  below.  For  convenience  of  reference  each  ore  is 
designated  by  number,  and  the  order  of  numbering  is  the  same 
throughout  this  paper.  Radium  values  representing  the  sum  of  two 
determinations  were  determined  by  the  complementary  method; 
those  determined  by  the  ignition  method  are  so  designated;  all  others 
were  determined  by  the  method  of  total  emanation  by  solution  hi  a 
single  operation. 

1.  Sample  of  65  pounds  from  Cripple  Creek  claim,  Long  Park,  Paradox  Valley,  Colo. 
U3O8  content:  2.10;  2.08,  and  2.12  per  cent;  average,  2.095  per  cent;  average  U  content, 
1.78  per  cent;  average  V205  content,  2.53  per  cent.    Ra  per  gram  X109:    5.94,  6.11, 
and  5.99  (ignition  method);  average,  6.02X10"9  gram.    Emanating  power,  29.6  per 
cent.     Ra/U=3.38X10-7. 

2.  Small  sample  from  the  Rajah  claim,  Roc  Creek,  Paradox  Valley,  Colo.    U808 
content:  33.19  and  33.24  per  cent;  average,  33.22  per  cent.    Average  U  content, 
28.18  per  cent;  average  V205  content,  14.05  per  cent.     Ra  per  gram  X108:    1.50+ 
8.71=10.21,1.67+8.34=10.01,  1.76+8.44=10.20;    average,  10.14X10-8gram.    Eman- 
ating power,  16.2  per  cent.    Ra/U=3.59X10~7. 

3.  Small  sample  from  Black  Fox  claim,  Bull  Canon,  south  of  Paradox  Valley,  Colo. 
U3O8  content:  1.63,  1.57,  1.60,  and  1.58  per  cent;  average,  1.595  per  cent.    Average 
U  content,  1.35  per  cent;  average  V205  content,  5.22  per  cent.    Ra  per  gram  X  10*: 
2.15+2.06=4.21,    4.29,    4.30,    4.23   (ignition   method);    average,   4.26X10^  gram. 
Emanating  power,  50.5  per  cent.    Ra/U=3.16X10~7. 

4.  Small  sample  from  Florence  claim,  Long  Park,  Paradox  Valley,  Colo.    U,08 
content:  23.54  and  23.42  per  cent;  average,  23.48  per  cent.    Average  U  content, 
19.92  per    cent;    average    V2O5     content,    10.63    per  cent.     Ra  per  gram  X 10*: 
1.404+5.861=7.27;  1.166+6.082=7.25;  7.33  (ignition  method);  average,  7.28X10""8 
gram.     Emanating  power,  17.7  per  cent.    Ra/U=3.66X10~7. 

5.  Small  sample  from  a  Curran  claim,  Long  Park,  Paradox  Valley,  Colo.    U3O8 
content:  24.03,  23.43,  24.75,  and  24.37  per  cent;  average,  24.25  per  cent.    Average 
U  content,  20.60  per  cent;  average  V2O5  content,  13.51  per  cent.    Ra  per  gramXIO8: 

'2.18+2.77=4.95;  2.36+2.62=4.98;  4.95;  4.97  (ignition  method);  average,  4.96X10-8 
gram.  Emanating  power,  45. 8  per  cent.  Ra/U=2.4lXlO~7. 

6.  Small  sample  of  a  concentrate  prepared  by  a  method  which  may  possibly  have 
affected  the  Ra/U  ratio.    Hence  the  data  for  this  sample  are  not  included  in  Table  I. 
U3O8  content:  9.20  and  9.05  per  cent;  average,  9.125  per  cent.    Average  U  content, 
7.74  per  cent;   average  V205  content,  10.08  per  cent.     Ra  per  gramXIO8:    2.166; 
2.167;  2.184  (ignition  method);  average,  2.17X10"8  gram.     Emanating  power,  30.4  per 
cent.     Ra/U=2.80XlO-7. 

7.  Small  sample  from  Florence  claim,  Long  Park,  Paradox  Valley,  Colo.    U3O8  con- 
tent: 3.16,  3.17,  3.23,  and  3.19  per  cent;  average,  3.185  per  cent.    Average  U  content, 
2.70  per  cent;  average  V2O5  content,  4.82  per  cent.    Ra  per  gramXIO9:    4.26+6.35= 
10.61;    10.86;    10.58;    10.60;    10.94  (ignition  method);    average,  10.72X10~9  gram. 
Emanating  power,  39.7  percent.     Ra/U=3.97X10-?. 

8.  Sample  of  3,016  pounds  from  a  Cummings  claim,  Bull  Canyon,  south  of  Paradox 
Valley,  Colo.    U308  content:  4.78,  4.72,  4.62,  and  4.61  per  cent;  average,  4.68  per  cent. 


24  THE   RADIUM-URANIUM    RATIO  IN   CARNOTITES. 

Average  U  content,  3.97  per  cent;  average  V2O5  content,  4.10  per  cent.  Ra  per  gram 
X109:  4.38+8.93=13.31;  4.45+8.50=12.95;  12.42;  12.90  (ignition  method);  13.67; 
average  13.05  XlO"9  gram.  Emanating  power,  33.9  per  cent.  Ra/U=3.29XlO~7. 

9.  Sample  of  29,118  pounds  from  same  locality  as  No.  8.    U3O8  content:  1.52,  1.57, 
and  1.48  per  cent;  average,  1.523  per  cent.    Average  U  content,  1.29  per  cent; 
average  V20S  content,  4.00  per  cent.     Ra  per  gramXlO9:    1.052+3.294=4.35;  0.719+ 
3.500=4.22;  4.43;  4.41    (ignition   method);  average,   4.35X10"9   gram.    Emanating 
power,  20.4  per  cent.     Ra/U=3.42XlO~7. 

10.  Sample  of  about  4,000  pounds  from  same  place  as  No.  5.    U3O8  content:  2.31, 
2.45,  2.35,  and  2.48  per  cent;  average,  2.40  per  cent.    Average  U  content,  2.04  per 
cent;  average  V2O5  content,  5.27  per  cent.    Ra  per  gramXlO9:    7.23;  7.40;  7.30 
(ignition  method);  average,   7.31X10"*  gram.    Emanating  power,   29.0  per  cent. 
Ra/U=3.58X10-7. 

'  11.  Small  sample  from  Melrose  claim,  Green  River  district,  Utah.  U308  content: 
4.14,  4.11,  4.12,  and  4.16  per  cent;  average,  4.13  per  cent.  Average  U  content,  3.50 
per  cent;  average  V2O5  content,  5.07  per  cent.  Ra  per  gramXlO9:  4.83+5.74=10.57; 
5.05+5.73=10.78;  11.12;  10.87;  11.41  (ignition  method);  average*  10.95 X10"9  gram. 
Emanating  power,  45.1  per  cent.  Ra/U=3.13X10~7. 

[12.  (Standard)  pitchblende  from  Kirk  mine,  Gilpin  County,  Colo.  U308  content: 
76.40  and  76.58  per  cent;  average,  76.50  per  cent.  Average  U  content,  64.9  per  cent. 
Ra  per  gram:  2.16X10"7  (calculated  from  Heimann  and  Marckwald'so  Ra/U  ratio  of 
3.328X10"7).  Emanating  power  2.7  per  cent,  by  two  determinations  of  5.98X10"9 
and  5.73X10"9  curies,  respectively.] 

13.  Sample  of  a  carload  lot  (about  30  tons)  from  the  claims  of  the  Crucible  Steel 
Co.,  Paradox  Valley,  Colo.    U308  content:  2.74  and  2.82  per  cent;  average,  2.78  per 
cent.    Average  U  content,  2.36  per  cent;  average  V206  content,  4.67  per  cent.     Ra  per 
gramXlO9:    3.51+4.32=7.83;    7.89    (ignition   method);    average,    7.86X10"-*    gram. 
Emanating  power,  44.7  per  cent.     Ra/U=3.34XlO~7. 

14.  Sample  of  a  carload  lot  (about  25  tons)  from  the  same  locality  as  No.  13. 
U3O8  content:  3.91  and  3.95  per  cent;  average,  3.93  per  cent.    Average  U  content, 
3.33  per  cent;  average  V205  content,  5.12  per  cent.     Ra  per  gramXlO9:    3.90+7.19= 
11.09;  11.09;  average,  11.09X10"9  gram.    Emanating  power,  35.2  per  cent.    Ra/U= 
3.33X10~7. 

15.  Sample  of  a  carload  lot  (about  20  tons)  from  same  locality  as  No.  13.    U3O8 
content:  2.85  and  2.82  per  cent;  average,  2.835  per  cent.     Average  U  content,  2.41  per 
cent;  average  V205   content,  4.72    per   cent.     Ra   per  gramXlO9:    3.488+4.467= 
7.955;  8.076;  average,  8.02X10"9  gram.     Emanating  power,  43.4  per  cent.     Ra/U= 
3.33  X10~7. 

16.  Sample  of  a  carload  lot  (about  22  tons)  from  same  locality  as  No.  13.    U308 
content:  2.52  and  2.54  per  cent;  average,  2.53  per  cent.     Average  U  content,  2.16  per 
cent;  average  V2O5  content,  3.75  per  cent.     Ra  per  gramXlO9:     3.191+3.916=7.107; 
7.077;  7.219  (ignition  method);  7.174;  average,  7.14X10~9gram.     Emanating  power, 
44.9  per  cent.     Ra/U=3.32x'lO~7. 

17.  Sample  of  a  carload  lot  (about  19  tons)  from  same  locality  as  No.  13.    U30s 
content:  3.05,  3.03,  and  3.06  per  cent;  average,  3.05  per  cent.    Average  U  content, 
2.59  per  cent;  average  V205  content,  4.66  per  cent.     Ra  per  gramXlO9:    8.66;  8.65 
(ignition  method);   average,   8.66X10"9  gram.     Emanating  power,    47.7  per  cent. 
Ra/U=3.34X10~7. 

18.  Small  sample  from  Kelly  No.  3  lode,  west  of  Mclntyre  district,  Colorado,  near 
Utah-Colorado  boundary.    U308  content:  25.63  and  25.71  per  cent;  average,  25.67  per 
cent.    Average  U  content,  21.77  per  cent;  average  V2O5  content,  22.3  per  cent.     Ra 

a  Heimann,  Berta,  and  Marckwald,  W.,  tiber  den  Radiumgehalt  von  Pechblenden:  Jahrb.  Radioakt. 
Elektronik,  Bd.  10, 1913,  p.  299;  Physik.  Ztschr.,  Bd.  14, 1913,  p.  303. 


BESULTS  OF   EXPERIMENTS.  25 

per  gramXIO8:    1.224+6.156=7.38;  7.34;  7.37  (ignition  method);  average,  7.36X10-* 
gram.     Emanating  power,  16.6  per  cent.     Ra/U=3.38X10~7. 

19.  About  60  pounds  of  a  composite  sample  of  several  ores.    U308  content:  3.18, 
3.26,  3.17,  and  3.10  per  cent;  average,  3.18  per  cent.    Average  U  content,  2.70  per  cent- 
average  V205  content,  4.03  per  cent.    Ra  per  gramXIO9:    8.902  (ignition  method); 
8.935;    average,    8.92X10"9   gram.      Emanating   power,    33.5    per   cent.    Ra/U= 
3.30X10"7. 

20.  Small  sample  from  Horse  Mountain,  Eagle  County,  Colo.    U308  content:  7.81 
and  7.75  per  cent;  average,  7.78  per  cent.'    Average  U  content,  6.60  per  cent;  average 
V205  content,  8.80  per  cent.     Ra  per  gramXIO9:    9.85+19.77=29.62;  29.91;  30.62; 
30.98  (ignition  method);  average,  30.3 X10"9  gram.     Emanating  power,  29.6  per  cent 
Ra/U=4.59X10-7. 

21.  Small  sample  from  a  Meyer  claim,  South  Park,  Colo.    U308  content:  9.52  and 
9.20  per  cent;  average,  9.36  per  cent.    Average  U  content,  7.94  per  cent;  average 
V2O5  content,  3.85  per  cent.    Ra  pergramXIO8:    1.07+1.31=2.38;  2.36;  2.37  (ignition 
method);  average,   2.37X10"8  gram.     Emanating  power,   45.2  per  cent.    Ra/U= 
2.99X10"7. 

22.  A  lot  of  several  hundred  pounds  from  the  Wade  and  Taylor  claims,  Pac  Creek, 
near  Moab,  Utah.    U3O8  content,  7.52  per  cent;  U  content,  6.38  per  cent;  average 
V2O5  content,  11.23  per  cent.     Ra  per  gramXIO8:    0.344+1.764=2.11;  2.12;  2.15 
(ignition  method);  average,  2.13X10"8.    Emanating  power,  16.2  per  cent.    Ra/U= 
3.34X10-7. 

23.  Sample  of  1,120  pounds  from  the  same  locality  as  No.  22.    U3O8  content,  11.62 
per  cent;  U  content,  9.86  per  cent.     Ra  per  gramXIO8:    3.29;  3.26  (ignition  method); 
average,  3.28X10"8  gram.     Emanating  power,  25.1  per  cent.     Ra/U=3.33X10~7. 

24.  Sample  of  about  1  ton  of  ore  of  unknown  origin,  very  finely  ground,  possibly  a 
mill  product  that  had  been  mixed  with  a  low-grade  carnotite  after  the  radium  had 
been  largely  removed.    U308  content:  8.83  and  8.85  per  cent;  average,  8.84  per  cent. 
Average  U  content,  7 .50  per  cent;  average  V205  content,  6.87  per  cent.     Ra  per  gramX 
109:   3.99;  3.88;  4.24  (ignition  method);  average,  4.04X10^ gram.    Ra/U=0.54X10-7. 

The  reasons  for  doubting  this  sample  to  be  a  natural  carnotite  ore  are  rather  numer- 
ous. Its  Ra/TJ  ratio  is  abnormally  low,  and  its  origin  could  not  be  ascertained. 
Under  the  microscope  it  shows  a  network  of  crystalline  needles  partly  soluble  in 
water  (apparently  CaS04),  such  as  could  not  have  existed  in  the  original  ore,  but  must 
have  formed  after  the  ore  was  ground,  because  their  length  is  several  times  the  average 
diameter  of  other  particles.  On  ignition  considerable  sulphur  is  distilled  off,  probably 
owing  to  reduction  of  sulphates  by  organic  matter.  For  these  reasons  the  authors  do 
not  believe  it  to  be  a  natural  carnotite,  and  have  presented  the  data  for  whatever 
general  interest  they  may  have,  without  including  them  in  Table  1. 


THE   RADIUM-URANIUM   RATIO  IN   CARNOTITES. 


A  summary  of  the  results  obtained  in  the  experiments  with  car- 
no  tite  ores  is  presented  in  Table  1  following: 

TABLE  I. — Results  of  experiments  with  carnotites. 


Percent- 

Grams of 

Radium- 

age  of 
normal 

No.  of 

Locality. 

U,08. 

U. 

radium 
X109  per 

Emanat- 
ing 

uranium 
ratio. 

ratio 
(pitch- 

ore. 

gram  of 

power. 

Ra 

blende 

ore. 

TJ     X10    . 

ratio= 

100  per 
cent).o 

Perct. 

Perct. 

Per  cent. 

5 

Long  Park,  Colo  

24.25 

20.6 

49.6 

45.8 

2.41 

72.4 

21 

South  Park,  Colo  

9.36 

7.94 

23.7 

45.2 

2.99 

89.8 

11 

Green  River,  Utah  

4.13 

3.50 

10.95 

45.1 

3.13 

94.0 

3 

8 

Bull  Canyon,  Colo  
Do 

1.60 
4  68 

1.35 
3  97 

4.26 
13  05 

50.5 
33  9 

3.16 
3.29 

94.9 

*98  8 

19 

3.18 

2.70 

8.92 

33.5 

3.30 

99.1 

16 

Long  Park,  Colo  

2.53 

2.16 

7.14 

44.9 

3.32 

*99.7 

14 

3.93 

3.33 

11.09 

35.2 

3.33 

*100.0 

15 

Do 

2.84 

2.41 

8.02 

43.4 

3.33 

*100  0 

23 

Moab  Utah 

11  62 

9  86 

32  8 

25  1 

3  33 

*100  0 

13 

Long  Park,  Colo  

2.78 

2.36 

7.86 

44.7 

3.34 

*100.3 

17 

Do  

3.05 

2.59 

8.66 

47.7 

3.34 

*100.3 

22 

Moab  Utah 

7  52 

6  38 

21  3 

16  2 

3  34 

*100  3 

18 
1 

Mclntyre  district,  Colo  
Long  Park  Colo 

25.67 
2  10 

21.77 
1  78 

73.6 
6  02 

16.6 
29  6 

3.38 
3  38 

101.5 
101  5 

9 

Bull  Canyon,  Colo  

1.52 

1.29 

4.35 

20.4 

3.42 

*102.  7 

10 

Long  Park,  Colo  

2.40 

2.04 

7.31 

29.0 

3.58 

*107.  5 

2 

Paradox  Valley  Colo 

33  22 

28  18 

101  4 

16  2 

3  59 

107  8 

4 

Long  Park,  Colo  

23.48 

19.92 

72.8 

17.7 

3.66 

109.9 

7 

Do....  

3.19 

2.70 

10.72 

39.7 

3.97 

119.2 

20 

Eagle  County,  Colo  

7.78 

6.60 

30.3 

29.6 

4.59 

137.8 

101  8 

a  In  results  preceded  by  an  asterisk  the  sample  represents  a  large  quantity  of  ore  (from  several  hundred 
pounds  to  25  tons). 
6  Composite  of  several  ores. 

DISCUSSION   OF  RESULTS. 

On  inspecting  the  last  two  columns  of  Table  I  there  appears  to  be 
only  one  possible  conclusion  as  to  the  radium-uranium  ratio  of  car- 
notite;  namely,  that  it  is  identical  with  that  of  pitchblende  in  all 
large  quantities  of  well-sampled  ore.  This  appears  to  be  true  regard- 
less of  the  locality  of  the  deposit  or  the  composition  of  the  ore.  The 
low  and  high  ratios  are  found  only  in  samples  representing  small 
quantities  of  ore,  and  the  variations  are  apparently  due  to  local 
transposition  of  radium  within  the  ore  bed;  they  are  completely 
equalized  on  sampling  sufficient  quantities  of  ore.  The  authors  are 
not  prepared  to  go  further  into  the  nature  of  this  transposition  at  the 
present  time,  because,  as  already  stated,  the  samples  were  not  col- 
lected with  this  object  in  view. 

Of  course,  the  fact  that  the  average  of  all  ratios  in  Table  I  should  be 
within  2  per  cent  of  the  normal  ratio  is  somewhat  accidental;  but 
that  the  average  for  all  the  large  samples  is  within  1  per  cent  of  the 
normal  ratio  appears  by  no  means  accidental,  and  seems  to  represent 
about  the  average  of  the  limits  of  experimental  error. 


RESULTS   OF   EXPERIMENTS.  27 

The  question  naturally  presents  itself  as  to  whether  high  and  low 
ratios  for  other  minerals  can  be  explained  in  the  same  way  as  for  car- 
notite.  As  far  as  we  are  aware  it  is  true  that  determinations  of  the 
radium-uranium  ratio  have  been  made,  in  all  the  minerals  examined, 
on  small  samples  only.  On  the  other  hand,  it  is  to  be  recalled  that 
high  ratios  had  not  been  hitherto  reported  except  for  primary  min- 
erals, which  are  not  affected  as  much  by  the  action  of  water  as  sec- 
ondary minerals  are. 

Furthermore,  in  the  case  of  autunite,  in  which  leaching  certainly 
does  produce  very  low  ratios,  no  high  ratios  have  ever  been  found  to 
support  the  transposition  theory  as  put  forward  for  carnotite.  In 
such  instances  it  has  been  found  that  the  leaching  process  removes  the 
radium  completely  from  association  with  the  original  uranium  parent, 
disseminating  it  widely  or,  in  exceptional  cases,  forming  deposits  con- 
taming  considerable  radium  with  no  uranium,  as  found  by  Danne0  hi 
a  specimen  of  pyromorphite  from  Issy  L'Eveque. 

The  difference  in  the  completeness  of  the  removal  of  radium  by 
leaching  exhibited  by  autunite  and  carnotite  may  be  due  to  the  fact 
that  the  latter  occurs  hi  a  region  of  very  low  rainfall;  in  fact,  aridity 
seems  to  be  a  necessary  condition  for  the  existence  of  carnotite. 
Under  such  conditions  and  in  view  of  the  fact  that  the  extent  of 
many  carnotite  deposits  is  large,  a  transposition  of  radium  might  be 
expected  rather  than  a  complete  removal. 

The  high  degree  to  which  carnotite  gives  up  its  emanation  by 
diffusion  as  shown  in  Table  1  and  discussed  on  pages  10  to  12,  appears 
rather  remarkable.  The  property  does  not  seem  to  be  connected 
with  any  other  known  properties  of  the  ores  and  the  authors  are  not 
able  at  present  to  do  more  than  call  attention  to  the  fact,  and  also 
to  note  that  carnotite  appears  to  furnish  in  the  solid  state  a  more 
abundant  source  of  radium  emanation  than  any  other  mineral  with 
the  same  radium  content. 

In  conclusion  it  may  be  stated  that  from  this  investigation  there 
seems  to  be  no  justification  for  regarding  the  radium-uranium  ratio 
in  commercial  quantities  of  carnotite  as  being  low  or  in  any  way  ab- 
normal. The  practice  of  evaluating  the  ore  from  its  uranium  content 
appears  to  be  correct  within  the  limits  of  reliability  of  uranium  de- 
terminations. In  a  later  paper  the  authors  expect  to  show  that  it 
will  be  more  convenient  as  well  as  accurate  to  determine  radium 
directly  than  to  use  the  indirect  method  of  a  uranium  analysis.  It 
is,  of  course,  needless  to  say  that  the  latter  procedure  must  always  be 
the  recourse  when  the  genuineness  of  the  product  is  uncertain  or  any 
other  abnormality  is  suspected.  However,  in  the  case  of  a  com- 
mercial quantity  of  correctly  sampled  carnotite,  the  uranium  content 

o  Danne,  Jacques,  Sur  un  nouveau  mineral  radifere:  Compt.  rend.,  t.  140, 1905,  p.  241. 


28  THE    RADIUM-UEANIUM    BATIO   IN   CAENOTITES. 

of  which  is  accurately  known,  there  remain  no  grounds  whatsoever 
to  suspect  the  radium  content  as  being  any  less  than  in  the  proportion 
of  1  part  of  radium  to  3,000,000  parts  of  metallic  uranium. 

SUMMARY. 

1.  Samples  of  carnotite  representing  large  quantities  of  ore   (a 
few  hundred  pounds  to  several  tons)  show  a  radium-uranium  ratio 
identical  with  that  of  pitchblende  (3.33X10"7);  this  ratio  is  also  in 
accord  with  the  value  calculated  from  radiation  data. 

2.  Samples  from  small  quantities  of  ore  (hand  specimens  up  -to  a 
few  pounds)  tend  to  exhibit  abnormal  ratios.     In  one  instance  the 
ratio  was  as  low  as  2.48X1 0~7,  and  in  another  as  high  as4.6xlO~7. 

3.  The  most  plausible  explanation  for  these  abnormal  ratios  seems 
to  be  that  of  transposition  of  radium  within  the  ore  bed,  producing 
local  differences  which  are  equalized  in  large  samples. 

4.  The  "emanating  power"  of  carnotite  is  high,  and  varies  from  16 
to  50  per  cent. 

5.  In  order  to  obtain  concordant  results  by  the  Boltwood  emana- 
tion method  it  was  found  desirable  to  determine  the  emanation 
liberated  by  solution  in  the  same  sample  from  which  the  emanating 
power  had  just  been  determined,  thus  making  the  two  determina- 
tions strictly  "complementary." 

6.  Radium  may  be  easily  determined  in  one  operation  by  the  ema- 
nation method,  either  by  solution  or  by  ignition  from  tubes  in  which 
it  has  been  sealed  for  one  month  to  reach  equilibrium. 

7.  In  contrast  with  the  success  of  the  solution  and  the  ignition 
methods  for   de-emanating  carnotite,   the  method   of  fusion  with 
sodium    and    potassium    carbonates    and    the    fusion-and-solution 
method  both  gave  low  results  and  were  abandoned. 

ACKNOWLEDGMENT. 

The  authors  take  pleasure  in  acknowledging  their  indebtedness  to 
Prof.  R.  B.  Moore,  physical  chemist  of  the  Bureau  of  Mines,  for  his 
helpful  advice  during  this  investigation. 


PUBLICATIONS  ON  MINERAL  TECHNOLOGY. 

A  limited  supply  of  the  following  publications  of  the  Bureau  of 
Mines  is  temporarily  available  for  free  distribution.  Requests  for  all 
publications  can  not  be  granted,  and  to  insure  equitable  distribution 
applicants  are  requested  to  limit  their  selection  to  publications  that 
may  be  of  especial  interest  to  them.  Requests  for  publications  should 
be  addressed  to  the  Director,  Bureau  of  Mines. 

BULLETIN  3.  The  coke  industry  of  the  United  States  as  related  to  the  foundry,  by 
Richard  Moldenke.  1910.  32  pp. 

BULLETIN  12.  Apparatus  and  methods  for  the  sampling  and  analysis  of  furnace 
gases,  by  J.  C.  W.  Frazer  and  E.  J.  Hoffman.  1911.  22  pp.,  6  figs. 

BULLETIN  47.  Notes  on  mineral  wastes,  by  C.  L.  Parsons.    1912.    44  pp. 

BULLETIN  53.  Mining  and  treatment  of  feldspar  and  kaolin  in  the  southern  Appa- 
lachian region,  by  A.  S.  Watts.  1913.  170  pp.,  16  pis.,  12  figs. 

BULLETIN  64.  The  titaniferous  iron  ores  in  the  United  States,  their  composition 
and  economic  value,  by  J.  T.  Singewald,  jr.  1913.  145  pp.,  16  pis.,  3  figs. 

BULLETIN  67.  Electric  furnaces  for  making  iron  and  steel,  by  D.  A.  Lyon  and  R. 
M.  Keeney.  1913.  142  pp.,  36  figs. 

BULLETIN  70.  A  preliminary  report  on  uranium,  radium,  and  vanadium,  by  R.  B. 
Moore  and  K.  L.  Kithil.  1913.  100  pp.,  2  pis.,  2  figs. 

BULLETIN  71.  Fuller's  earth,  by  C.  L.  Parsons.    1913.    38  pp. 

BULLETIN  77.  The  electric  furnace  in  metallurgical  work,  by  D,  A.  Lyon,  R.  M. 
Keeney,  and  J.  F.  Cullen.  1914.  216  pp.,  56  figs. 

BULLETIN  81.  The  smelting  of  copper  ores  in  the  electric  furnace,  by  D.  A.  Lyon 
and  R.  M.  Keeney.  1914. 

BULLETIN  84.  Metallurgical  smoke,  by  C.  H.  Fulton.     1914.    90  pp.,  5  pis.,  15  figs. 

TECHNICAL  PAPER  15.  An  electrolytic  method  of  preventing  corrosion  of  iron  or 
steel,  by  J.  K.  Clement  and  L.  V.  Walker.  1913.  19  pp.,  10  figs. 

TECHNICAL  PAPER  31.  Apparatus  for  the«xact  analysis  of  flue  gas,  by  G.  A.  Burrell 
and  F.  M.  Seibert.  1913.  12  pp.,  1  fig. 

TECHNICAL  PAPER  36.  The  preparation  of  specifications  for  petroleum  products, 
by  I.  C.  Allen.  1913.  12  pp. 

TECHNICAL  PAPER  41.  The  mining  and  treatment  of  lead  and  zinc  ores  in  the 
Joplin  district,  Missouri;  a  preliminary  report,  by  C.  A.  Wright.  1913.  43  pp.,  5  figs. 

TECHNICAL  PAPER  50.  Metallurgical  coke,  by  A.  W.  Belden.  1913.  48  pp., 
Ipl.,  23  figs. 

TECHNICAL  PAPER  60.  The  approximate  melting  points  of  some  commercial  cop- 
per alloys,  by  H.  W.  Gillete  and  A.  B.  Norton.  1913.  10  pp.,  1  fig. 

TECHNICAL  PAPER  81.  The  vapor  pressure  of  arsenic  trioxide,  by  H.  V.  Welch  and 
L.  H.  Duchak.  1915.  22  pp.,  2  figs. 


Date  Due 


PRINTED     IN  U.  S.  A. 


THE  JLUBRARY 
UNIVERSITY  OF  CALIFORNIA 


UCLA-Geo,ogy/Geophy8ic8Ub 

TN948R3L6 


Syracuse,  N.    Y. 
Stockton,  Calif. 


(  UC  SOUTHERN  REGIONAL  LIBRARY  FACILITY 

AA    001274495    9 


^^        *•  ' 


